1. Field of the Invention
The present invention relates to a resin composition for foaming and a foamed article made thereof, and more particularly, to a resin composition for foaming with a foaming property improved by applying a biodegradable polyester resin containing a monomer of a double bond compound to an ethylene-vinyl acetate (EVA) resin as a polymer for foaming, and a foamed article made thereof with excellent properties.
2. Discussion of Related Art
Synthetic resin-based foamed articles that are usefully used are made of various materials such as polyethylene, polypropylene, an ethylene-vinyl acetate copolymer, polyester, and polyurethane.
Among those, an ethylene-vinyl acetate resin-based foamed article is produced by various molding methods such as a typical press foam molding method and an injection foam molding method. Since the ethylene-vinyl acetate resin-based foamed article is light and cheap, but does not discolor, it has widely been used.
An important technical matter for the foamed article is eco-friendly manufacturing plastic which has an excellent processability without a decrease in mechanical property This is urgently demanded technique condition for manufacturing a foamed article. Conventionally, if a cross-linking foamed article using a composition for foaming comprising an ethylene-vinyl acetate resin, azodicarbonamide, and organic peroxide is discarded and buried in the ground, it is hardly biodegraded. If the cross-linking foamed article is incinerated, the harmful gases such as dioxin or VOC are generated. Therefore, it is likely to disturb the ecosystem by destruction of the environment or the like.
Accordingly, a mixture of a biodegradable polymer resin and an ethylene-vinyl acetate resin has been used to introduce eco-friendly bio plastic. However, by way of example, a foamed article comprised of a mixture of polylactic acid and an ethylene-vinyl acetate resin has a low compatibility with the ethylene-vinyl acetate resin, so that the foamed article cannot have a desired form, for example, a foaming property such as a uniform foam size, resulting in a decrease in mechanical property. In particular, polylactic acid has many problems in that, for example, it cannot be processed at a typical process temperature due to its high melting temperature and a low thermal property.
There have been carried out studies to solve conventional problems with a cross-linking foamed article using a composition for foaming based on a mixture of an ethylene-vinyl acetate resin and other resins in various ways. However, such a cross-linking foamed article does not have a sufficient performance.
By way of example, a foaming property is improved by using a mixture of an ethylene-vinyl acetate resin as a polymer for foaming with a catalytic cross-linking agent (dicumyl peroxide) as a cross-linking supplemental agent, a co-crosslinking agent (triallyl cyanurate), and a foaming agent (azodicarbonamide). However, even in such a case, if a mixture of an ethylene-vinyl acetate resin with a biodegradable polyester resin of 25% or more is used, processability decreases. After a chemical cross-linking, a foaming property of the biodegradable polyester resin is partially expressed independently from the ethylene-vinyl acetate resin, resulting in deterioration of a foam size and a shape of a foamed article. As described above, there are still problems with the biodegradable polyester resin.
Therefore, there has urgently been demanded a good foamed article which is not only eco-friendly but also improved in foaming and mechanical property.
In this regard, the present inventors researched a resin composition for foaming, and as a result, found that if a biodegradable polyester resin containing a monomer of a double bond compound is mixed with an ethylene-vinyl acetate resin, the double bond included in the biodegradable polyester resin is chemically cross-linked to the ethylene-vinyl acetate resin by a cross-linking agent, resulting in improvement in compatibility, so that processability and a foaming property can be improved and further a mechanical strength of a foamed article can be improved. Thus, the inventors finally completed the present invention.